The purpose of drug delivery systems in cancer chemotherapy is to achieve selective delivery of anti-cancer agents to cancer tissue at an effective concentrations for the appropriate duration of time, so that we may be able to reduce the adverse effects of a drug and simultaneously enhance the anti-tumor effect. Polymeric micelles were expected to increase the accumulation of drugs in tumor tissues utilizing the enhanced permeability and retention effect and to incorporate various kinds of drugs into the inner core by chemical conjugation or physical entrapment with relatively high stability. The size of the micelles can be controlled within the diameter range of 20–100 nm, to ensure that the micelles do not pass through normal vessel walls; therefore, a reduced incidence of the side effects of the drugs may be expected due to the decreased volume of distribution. There are several anti-cancer agent-incorporated micelle carrier systems under clinical evaluation. Phase 1 studies of a cisplatin-incorporated micelle, NC-6004 and an SN-38-incorporated micelle, NK012, are now underway. A Phase 2 study of a paclitaxel-incorporated micelle, NK105, against stomach cancer is also underway.